Dear all,
I am working on experimental data of a spar buoy wind turbine. OC3 Hywind 5MW turbine is taken as reference. I am calibrating the physical model starting from the certified test 24.
I have some problem comparing the tensions of the mooring lines coming from the summary output and the ones from MoorDyn output. The values from the global summary output seem to be affected by a magnification factor of 10^3 in respect the specific MoorDyn output.
Should I consider in input the tension in N or KN? Is it possible that the labels in the general output are wrong even for the displacements? It appears as though all the output parameters are affected by this problem.
I was wondering if I am making a mistake in the input files of MoorDyn and Hydrodyn (here attached).
Do you have any thoughts on what could be the cause of this problem?
I really appreciate your help
Best regards,
Luigia Riefolo
hydrodyn.pdf (71.9 KB)
moordyn.pdf (53 KB)
Dear Luigia,
I’m sorry, but I’m not sure what you mean when you refer to “global summary output” versus “MoorDyn output”. Please clarify what problem you have.
Best regards,
Dear Jason,
sorry if I was no clear. My question is related to the output of mooring tensions and displacements.
I am not sure if the mooring tensions from MoorDyn are in KN or N as reported in the label.
Looking at the two output from MoorDyn, the results have a magnification factor of 10^3.
Thank you in advance for your help
Best regards,
Luigia
Dear Luigia,
The mooring tensions from MoorDyn are output in N, not kN.
What do you mean by the “two output from MoorDyn”?
Best regards,
Dear Jason,
thank you for your reply.
As you can see from the data here attached, the tensions from the MoorDyn outputs of the same test are different with a factor of 10^3.
Is it possible that for an unknown reason the general output with all the simulated parameters (displacements, water elevation, rotations etc.) have a different unit in respect to the input parameters?
Sorry me but the question is complicated to explain.
I hope that this time my doubt is clearer than the previous post.
Thanks for your time
Best regards,
Luigia
Dear Luigia,
The outputs directly from MoorDyn, including the “N” units, seem to be the correct ones in this case. 9E5 N is the right order of magnitude.
I’ll look through the code and see if I have an error in how MoorDyn passes the fairlead tensions to FAST. Did you mention that there was something wrong with labels for displacements as well? (Please explain if so.)
Thanks for pointing out this discrepancy. I’ll try to fix it for the next update.
Best regards,
Matt
Dear Matt,
thank you for your precious help.
Yes, even for displacements, rotations and water elevation in the WRP (0, 0) the values have a different unit with a magnification factor of 10 (please see the enclosed table).
This discrepancy could be due by some error in the input files or in the output’s label?
The results are related to the following wave characteristics: WaveHs=4 m and Tp =11.4 s.
Thanks a lot
Best regards,
Luigia
Dear Luigia,
I’ve not seen the same problem when I run FAST–the units in the general (FAST), HydroDyn, and MoorDyn output files are consistent. Have you modified the source code in some way?
Best regards,
Dear Jason,
I have modified the orientation of the mooring lines in MoorDyn, the wave characteristics in HydroDyn and in ElastoDyn the tower nodes to have the tower displacements at the selected strain gages. I run regular waves under steady wind. In the first post I attached the input files for MoorDyn and HydroDyn modules.
I really appreciate your help
Best regards,
Luigia
Dear Luigia,
Please upload the *.out files (or at least the first several lines).
Best regards,
Dear Jason,
thanks again for your time.
Please, in the attachments you can find the outputs from MoorDyn and HydroDyn.
Best regards,
Luigia
output files.rar (3.28 MB)
Dear Luigia,
You didn’t include the FAST *.out file in your archive so I can’t check the consistency in the units between the files. I do notice, though, that the magnitude of the platform motions in the attached HydroDyn file are much smaller than what you directly included in your post above e.g. at time=0.0125 s, WRPSurge = -3.95E-5 m in the attached HydroDyn output file instead of -3.95E-1 m in your post above. Are you sure the data you included directly into your post above are correct?
Best regards,
Dear Jason,
please in the zip file you can find the output files. The general output (in txt) is not completed because the file is too large.
Thanks again for your help
Best regards,
Luigia
output files run 300s.rar (2.02 MB)
Dear Luigia,
The FAST *.out file you attached (renamed to _out.txt) looks a bit odd to me. Did you reformat this file via post-processing in some way? Can you send me the first 20 rows of the file exactly as output by FAST? What have you set OutFmt to in the FAST primary input file?
Best regards,
Dear Jason,
I didn’t post-processed the output file. I set the OutFmt of the primary input to 3.
Here I attached the first rows of the output.
Thank you very much for your help
Best regards,
Luigia
summary_test.rar (9.01 KB)
Dear Luigia,
The FAST data in the *.out file you attached does indeed match the *.out data you’ve attached from HydroDyn and MoorDyn. It is the data in the *_out.txt file that differs. It seems that the source of your problem is how the data was transferred from the *.out to _out.txt.
Best regards,
Dear Jason,
thank you very much for your help. The problem, in fact, came up when I transferred the data from .out to .txt or .xls. Now I decided to work directly through Matlab software. Finally I have the results with the correct units.
I really appreciate your support!
Best regards,
Luigia
